DESCRIPTION: The investigators have described individual differences in infant behavior and a corresponding pattern of brain electrical activity (EEG) both associated with particular styles of infant and child temperament. Studies indicate that the pattern of EEG recorded over the anterior portion of the frontal lobes may be an important marker of individual differences in the tendency to express positive or negative emotions. This pattern has particular significance for the development of social withdrawal. Infants who exhibit wariness and behavioral inhibition during the infancy period and who display greater relative right frontal EEG activation are more likely to be socially withdrawn during peer interaction at the preschool period. The combination of infant behavior and EEG measured physiology is the best predictor of social competence and withdrawal in four year old children. The two studies proposed in the current grant are designed to extend our work in a number of ways: first, we will examine the stability and predictive validity of both behavior and physiology in the elementary school years. Second, they will be able to validate the importance of early infant temperament and physiology in predicting seven year old social competence. Specifically, with a large sample of subjects, selected at four months of age for specific infant temperament characteristics, the investigators will examine the continuities and discontinuities in behavioral style through the child's entry into elementary school. Due to the repeated psychophysiological assessment of the children in these cohorts and the relatively low attrition rate we will be able to examine the independent and interactive roles of brain electrical activity in predicting social withdrawal or social competence. In addition, they propose to study infants who represent the opposite end of the temperamental spectrum: extremely inhibited infants. Extremely uninhibited infants themselves may represent a unique temperamental group who are highly sociable in their interactions. Among this group we intend to study a sub-group of children who are unable to modulate their positive, exuberant behaviors and who are easily frustrated and angered in response to mild stress. The current grant proposal contains two studies: one represents the continued study of children on whom there are both behavioral and physiological data associated with behavioral inhibition, reticence, and social withdrawal. The second study will examine the developmental outcomes of extremely uninhibited infants charting the incidence of maladaptive behavior among these children.